Figure 1.

Alternative splicing of bcl-x. (A) Schematic representation of the bcl-x gene and of the bcl-xL and bcl-xS alternatively spliced transcripts. Cis-regulatory sequences that act as splicing enhancers or silencers are indicated. The in vitro splicing construct used in this study, pBK-bclx, is schematically represented. (B) In vitro splicing of pBK-bclx. Radiolabeled pre-mRNA substrates were incubated in HeLa nuclear extract. RNA precursors and spliced products are indicated by the schematics. The ratio of bcl-xL to -xS observed is shown. (C) Endogenous bcl-x expression in HeLa cells. The ratio of bcl-xL/-xS in HeLa cells was determined by RT–PCR. Splicing ratios and error bars have been obtained from three independent experiments.